Fainting - A Guide

Fainting is a sudden, temporary loss of consciousness that usually results in a fall. Consciousness is usually regained within a minute or two

Overview

Healthcare professionals often use the term "syncope" when referring to fainting, because it distinguishes fainting from other causes of temporary unconsciousness, such as seizures (fits) or concussion.

In most cases, when a person faints, they'll regain consciousness within a minute or two. However, less common types of fainting can be medical emergencies.

Dial 999 to request an ambulance if a person who has fainted doesn't regain consciousness within two minutes.

What causes a faint?

To function properly, the brain relies on oxygen that's carried in the blood. Fainting can occur when the blood flow to the brain is reduced.

Your body usually corrects reduced blood flow to the brain quickly, but it can make you feel odd, sweaty and dizzy. If it lasts long enough, you may faint.

There are various reasons for a reduction in blood flow to the brain, but it's usually related to a temporary malfunction in the autonomic nervous system. This is the part of your nervous system that regulates the body's automatic functions, including heartbeat and blood pressure. This type of fainting is called "neurally mediated syncope".

Neurally mediated syncope can be triggered by emotional stress, pain or prolonged standing. It can also be caused by physical processes such as coughing, sneezing or laughing.

What to do if you or someone else faints

If you feel you're about to faint, lie down, preferably in a position where your head is low and your legs are raised. This will encourage blood flow to your brain.

If it's not possible to lie down, sit with your head between your knees. If you think someone is about to faint, you should help them to lie down or sit with their head between their knees.

If a person faints and doesn't regain consciousness within one or two minutes, put them into the recovery position.

To do this:

place them on their side so they're supported by one leg and one arm

open their airway by tilting their head back and lifting their chin

monitor their breathing and pulse continuously

You should then dial 999, ask for an ambulance and stay with the person until medical help arrives.

Symptoms of Fainting

When you faint, you'll feel weak and unsteady before passing out for a short period of time, usually only a few seconds.

Fainting can occur when you're sitting, standing, or when you get up too quickly.

Warning symptoms

You may not experience any warning symptoms before losing consciousness, and if you do it may only be for a few seconds.

You may experience the following symptoms just before losing consciousness:

yawning

a sudden, clammy sweat

nausea (feeling sick)

fast, deep breathing

confusion

lightheadedness

blurred vision or spots in front of your eyes

ringing in your ears

This will usually be followed by a loss of strength and consciousness.

When you collapse to the ground, your head and heart are on the same level. This means that your heart doesn't have to work as hard to push blood up to your brain. You should return to consciousness after about 20 seconds.

Dial 999 and ask for an ambulance if someone faints and doesn't regain consciousness within two minutes.

After fainting

After fainting, you may feel confused and weak for about 20-30 minutes. You may also feel tired and not be able to remember what you were doing just before you fainted.

Fainting or stroke?

Fainting can sometimes be mistaken for a serious medical condition, such as a stroke. A stroke is a medical emergency that occurs when blood supply to the brain is interrupted.

You should dial 999 immediately and ask for an ambulance if you think that you or someone else is having a stroke.

The main symptoms of stroke can be remembered with the word FAST, which stands for Face-Arms-Speech-Time (see below).

Face– the face may have fallen on one side, the person may not be able to smile, or their mouth or eye may have drooped.

Arms – the person may not be able to raise both arms and keep them there, due to weakness or numbness.

Speech – the person may have slurred speech.

Time – it's time to dial 999 immediately if you see any of these signs or symptoms.

You should also dial 999 and ask for an ambulance if someone faints and doesn't regain consciousness after a minute or two.

Causes of Fainting

Fainting (syncope) is caused by a temporary reduction in blood flow to the brain.

Blood flow to the brain can be interrupted for a number of reasons. The different causes of fainting are explained below.

Autonomic nervous system malfunction

Fainting is most commonly caused by a temporary malfunction in the autonomic nervous system. This type of fainting is sometimes known as neurally mediated syncope.

The autonomic nervous system is made up of the brain, nerves and spinal cord. It regulates automatic bodily functions, such as heart rate and blood pressure.

An external trigger – such as an unpleasant sight, heat or sudden pain – can temporarily cause the autonomic nervous system to stop working properly, resulting in a fall in blood pressure and fainting.

It may also cause your heartbeat to slow down or pause for a few seconds, resulting a temporary interruption to the brain's blood supply. This is called vasovagal syncope.

Coughing, sneezing or laughing can sometimes place a sudden strain on the autonomic nervous system, which can also cause you to faint. This is called situational syncope.

The autonomic nervous system can also sometimes respond abnormally to upright posture. Normally, when you sit or stand up, gravity pulls some of your blood down into your trunk (torso) and your hands and feet.

In response, your blood vessels narrow and your heart rate increases slightly to maintain blood flow to the heart and brain, and prevent your blood pressure dropping. This results in a slight increase in blood pressure.

However, occasionally, standing or sitting upright can interrupt the blood supply to the heart and brain. To compensate, the heart races and the body produces noradrenaline (the "fight or flight" hormone).

Low blood pressure

Fainting can also be caused by a fall in blood pressure when you stand up. This is called orthostatic hypotension and it tends to affect older people, particularly those aged over 65. It’s a common cause of fallsin older people.

When you stand up after sitting or lying down, gravity pulls blood down into your legs, which reduces your blood pressure. The nervous system usually counteracts this by making your heart beat faster and narrowing your blood vessels. This stabilises your blood pressure.

However, in cases of orthostatic hypotension, this doesn't happen, leading to the brain's blood supply being interrupted and causing you to faint.

Possible triggers of orthostatic hypotension include:

dehydration – if you're dehydrated, the amount of fluid in your blood will be reduced and your blood pressure will decrease; this makes it harder for your nervous system to stabilise your blood pressure and increases your risk of fainting

diabetes – uncontrolled diabetes makes you urinate frequently, which can lead to dehydration; excess blood sugar levels can also damage the nerves that help regulate blood pressure

Diagnosing fainting

In some cases of fainting, you'll need to see a healthcare professional after the fainting episode to investigate whether there's an underlying health condition.

Your GP will be able to diagnose the cause and determine whether further investigation and treatment are needed.

When to see your GP

Most cases of fainting aren't a cause for concern and don't require treatment, but you should see your GP if you're at all concerned.

You should also see your GP after fainting and you:

have no previous history of fainting

experience repeated episodes of fainting

injure yourself during a faint

have diabetes – a lifelong condition that causes your blood glucose level to become too high

are pregnant

have a history of heart disease – where your heart's blood supply is blocked or interrupted

experienced chest pains, an irregular heartbeat or a pounding heartbeat before you lost consciousness

experienced a loss of bladder or bowel control

took longer than a few minutes to regain consciousness

During an assessment after a fainting episode, your GP will ask about the circumstances surrounding your fainting episodes and your recent medical history. They may also measure your blood pressure and listen to your heartbeat using a stethoscope.

Electrocardiogram (ECG)

If your GP thinks your fainting episode may have been caused by a heart problem, they may suggest that you have an electrocardiogram (ECG).

An ECG records your heart's rhythm and electrical activity. A number of small, sticky patches called electrodes are placed on your arms, legs and chest. Wires connect the electrodes to an ECG machine.

Every time your heart beats, it produces tiny electrical signals. The ECG machine traces these signals on paper, recording any abnormalities in your heartbeat.

An ECG is usually carried out at a hospital or GP surgery. The procedure is painless and takes about five minutes.

Carotid sinus test

If your GP thinks that your fainting episode was associated with carotid sinus syndrome, they may massage your carotid sinus to see whether it makes you feel faint or lightheaded.

The carotid sinus is a collection of sensors in the carotid artery, which is the main artery in your neck that supplies blood to your brain.

If the carotid sinus massage causes symptoms, it may indicate that you have carotid sinus syndrome (see causes of fainting for more information).

Blood tests

Blood tests may be carried out to rule out conditions such as diabetes or anaemia (a condition where the body doesn't produce enough oxygen-rich red blood cells).

Your GP may measure your blood pressure while you're lying down, and again after you stand up. You may have orthostatic hypotension if your blood pressure falls after you stand up.

If you have orthostatic hypotension, you may be asked further questions to help determine the cause. For example, it can sometimes occur as a side effect of taking some medications.

Next steps

If tests reveal an underlying cause of your fainting, such as a heart problem or orthostatic hypotension, your GP may recommend treatment for fainting

If you're diagnosed with a heart condition, you may need further tests and treatment. For example, several different medicines can be used to treat heart disease (where your heart's blood supply is blocked by a build-up of fatty substances in the main blood vessels).

Treating fainting associated with the nervous system

Most fainting episodes are associated with a temporary malfunction of the autonomic nervous system, which regulates the body's automatic functions, such as heartbeat and blood pressure. This type of fainting is called neurally mediated syncope.

Treatment for neurally mediated syncope involves avoiding any possible triggers. If you're not sure what caused your fainting episode, your GP may suggest keeping a diary of any symptoms you experience and making a note of what you were doing at the time you fainted, to help identify possible causes.

There are also steps you can take to avoid losing consciousness if you think that you may be about to faint (see above).

Fainting associated with an external trigger

Fainting can occur when an external trigger, such as a stressful situation, causes a temporary malfunction in your autonomic nervous system. This is called vasovagal syncope.

In most cases of vasovagal syncope, further treatment isn't required. However, you may find it useful to avoid potential triggers, such as stressor excitement, hot and stuffy environments, and long periods spent standing.

If you know that injections or medical procedures, such as blood tests, make you feel faint, you should tell the doctor or nurse beforehand. They'll make sure you're lying down during the procedure.

Fainting associated with bodily functions

Fainting can occur when a bodily function or activity – such as coughing – places a sudden strain on the autonomic nervous system. This is called situational syncope.

There's no specific treatment for situational syncope, but avoiding the triggers may help. For example, if coughing caused you to faint, you may be able to suppress your urge to cough and therefore avoid fainting.

Carotid sinus syndrome

Carotid sinus syndrome is where pressure on your carotid sinus causes you to faint. Your carotid sinus is a collection of sensors in the carotid artery, which is the main artery in your neck that supplies blood to your brain.

You can avoid fainting by not putting any pressure on your carotid sinus – for example, by not wearing shirts with tight collars.

In some people, carotid sinus syndrome can be treated by having a pacemaker fitted. A pacemaker is a small electrical device that's implanted in your chest to help keep your heart beating regularly.

Treating fainting associated with low blood pressure

Fainting can occur when your blood pressure drops as you stand up. This drop in blood pressure is called orthostatic hypotension.

For example, avoid becoming dehydrated by increasing your fluid intake. Your GP may also advise you to eat small, frequent meals, rather than large ones, and to increase your salt intake.

Taking certain medications can also decrease blood pressure. However, don't stop taking a prescribed medication unless your GP or another qualified healthcare professional in charge of your care advises you to do so.

Physical counterpressure manoeuvres

Physical counterpressure manoeuvres are movements that are designed to raise your blood pressure and prevent you losing consciousness. One study found that training in physical counterpressure manoeuvres can reduce fainting in some people.

Physical counterpressure manoeuvres include:

crossing your legs

clenching the muscles in your lower body

squeezing your hands into a fist

tensing your arm muscles

You need to be trained in how to carry out these movements correctly. You can then carry them out if you experience any symptoms that suggest you're about to faint, such as feeling lightheaded.

Driving

If you've fainted, it could affect your ability to drive. Depending on what caused you to faint, and whether you have any underlying health conditions, you may need to inform the Driver and Vehicle Licensing Agency (DVLA).

It's your legal obligation to inform the DVLA about a medical condition that could affect your driving ability. The GOV.UK website has more information about blackouts, fainting and driving.

Safety at work

If you've fainted, it may affect your safety at work or the safety of others. For example, continuing to operate machinery may be dangerous if it's likely that you'll faint again.

The healthcare professionals who diagnose and treat your condition can tell you whether it's likely to affect your work. If it is, speak to your health and safety representative.